1. Field of the Invention
This invention relates to novel anhydrous crystalline 9-(1,3-dihydroxy-2-propoxymethyl)guanine. The invention also relates to a process for preparing the novel crystalline form.
2. Related Disclosure
The compound 9-(1,3-dihydroxy-2-propoxymethyl)guanine also known as DHPG is a very potent antiviral agent. (See U.S. Pat. No. 4,355,032.) DHPG is known to exist as an unstable hydrate. This hydrate has serious disadvantages because it is hygroscopic at ambient humidity. The hygroscopic nature of DHPG hydrate causes handling and formulating problems.
Surprisingly, there has been discovered an extremely stable anhydrous crystalline DHPG which is unusually resistent to water absorption. This unusually stable form has better physical characteristics than the known DHPG hydrate. Because of its non-hygroscopic nature anhydrous crystalline DHPG retains a better physical appearance over a longer period of time. Any improvement in the physical appearance of a dosage form of a drug, of course, enhances both physician and patient acceptance and increases the likelihood of success of the treatment.
The resistance to water absorption results in reproducible batches of highly pure DHPG. Because of the high purity and extreme stability of anhydrous crystalline DHPG it is better suited to be used as a reference standard in HPLC analysis.